| The purpose of this research was to investigate the sub-chronic effects of environmentally realistic cadmium (Cd) concentrations on the reproductive and developmental axes and stress response of rainbow trout with the intention of furthering our understanding on the endocrine-disrupting mechanism(s) of action of this metal in teleosts.;Cd exposure has impaired three life-stages of trout: eggs, larvae and juveniles with juvenile being the most sensitive stage examined. The lowest concentrations used caused premature hatching and the highest caused delayed hatching. Interestingly final hatching success was not affected. 2.50 mug/L Cd negatively affected larval growth: larvae were shorter in length and weighed less compared to controls. Plasma sex steroid concentrations were increased in juveniles at all Cd concentrations after 28 days. The specific toxic site(s) of action of Cd on steroidogenesis was determined using an in vitro testicular cell preparation. Our results indicate that there are both stimulatory and inhibitory sites near the pituitary hormone receptor location, on the first steps of the pathway.;Similarly, the hypothalamus-pituitary-interrenals axis and stress response were both affected by Cd. Decreased plasma cortisol concentrations were observed at all concentrations from 7 to 40 days of exposure but they were not accompanied by interrenal impairment or alterations in other stress response parameters. However, interrenal steroidogenesis was impaired in a dose-dependent manner in vitro. One major inhibitory site(s) of action of Cd on the cortisol synthesis pathway is located after the pituitary hormone receptor location and prior to the cholesterol cleavage.;Negative effects of Cd at concentrations as low as 0.05 mug/L have never been reported in the literature. Since the guidelines for Cd are under review by the British Columbia Ministry of Environment, our results may add important data in determining new guideline values.;This study showed for the first time that very low Cd concentrations (0.05, 0.25, 0.50 and 2.50 mug/L) can result in a multifaceted toxicity paradigm, with important effects on the reproductive axis, and to a lesser extent on the stress response of rainbow trout.;Keywords. Cadmium, rainbow trout, reproduction, stress response, endocrine disruption. |
